Abrasion-resistant coating composition, process for making such coating composition and article coated therewith

ABSTRACT

The coating composition according to the invention comprises:  
     (A) a component which is the reaction product with oxalic acid of at least one organometallic compound of formula:  
     R y   1 —M (OR) x-y    (I)  
     wherein, M is a metal R is H or an alkyl radical, R 1  is a chelating ligand, x is the valency of the metal, y is an integer at least equal to 1 and x-y is at least equal to 1; and  
     (B) at least one organoalkoxysilane of formula:  
     R n   3 Si (OR 2 ) 4-n    (II)  
     wherein, R 2  is an alkyl radical, R 3  is an epoxidized alkyl group and n is an integer from 1 to 3 or a mixture of the organoalkoxysilane of formula (II) with an alkoxysilane of formula (II′)  
     R′ n′ Si(OR″) 4-n′   (II′)  
     wherein n′ is an integer from 0 to 3,  
     R″ is H, an alkyl radical or an alkoxyalkyl radical, and  
     R′ is a vinyl, (meth)acryl, aromatic, cyclic or aliphatic alkyl radical.  
     Application for making abrasion-resistant coating on plastic ophtalmic lenses.

BACKGROUND OF THE INVENTION

[0001] (1) Field of the Invention

[0002] The present invention relates in general to an abrasion-resistantcoating composition, as well as to a process for making such acomposition and articles, in particular optical articles such asophtalmic lenses, comprising an abrasion-resistant coating including acured layer of said abrasion-resistant coating composition.

[0003] (2) Description of the Prior Art

[0004] Numerous articles must be provided with abrasion-resistant orscratch resistant coatings since their sensitivity towards scratchingdoes not allows them to be used in practice or allows only short periodsof use.

[0005] This is in particular the case of optical articles such asophtalmic lenses for which an abrasion-resistant or scratch-resistantsurface is essential for maintaining a lens transparency over a periodof time as long as possible.

[0006] The use of transparent plastic materials for making opticalarticles such as ophtalmic lenses is nowadays common pratice due totheir unique lightness advantage compared to mineral glasses.Additionally, the use of such transparent plastic materials for makingoptical articles, in particular ophtalmic lenses, has allowedmanufacturing articles having high refractive indices of 1.6 or more.

[0007] As a result of this achievement, it has been possible tomanufacture lenses of lower thickness for an equivalent corrective power(optical power).

[0008] However, plastic materials in general, and more especially thoseemployed in the manufacture of ophtalmic lenses, usually have poormechanical surface characteristics with in particular low resistance toabrasion or scratching.

[0009] It is therefore a common practice to protect them with anabrasion-resistant or scratch-resistant coating.

[0010] Aqueous composition of organoalkoxisilanes and metal alkoxideshave been proposed for making such abrasion and scratch-resistantcoatings, as for example in U.S. Pat. Nos. 4,084,021; 4,746,366;4,754,012; 4,814,017 and 5,357,024.

[0011] Although these prior art compositions impart abrasion and scratchresistance to plastic substrates coated therewith there is still a need,in particular in the field of ophtalmic lenses, to formulate abrasionand scratch-resistant coating compositions exhibiting higher abrasionand scratch-resistance properties.

[0012] Furthermore, with the present possibility of obtainingtransparent plastic material substrates having a wide range ofrefractive indices, for example, from 1.45 to 1.65 and more, it would beof major interest to formulate abrasion and scratch-resistant coatingcompositions which would exhibit refractive indices matching such a widerange of refractive indices and in particular high refractive indices.

[0013] Increasing the amount of metal alkoxides, such as titanium andzirconium alkoxide in the aqueous compositions of organoalkoxysilanes ofprior art would increase the refractive indices of resulting curedcoatings. However, high contents of metal alkoxides in such coatingcompositions lead to stability problems of the formulated compositions.In particular, the metal alkoxides, when used in relatively high amountsin the coating compositions, have a pronounced tendency to precipitateand agglomerate, resulting in an non-homogeneous coating.

SUMMARY OF THE INVENTION

[0014] Thus, the aim of the present invention is to formulate anabrasion or scratch-resistant coating composition which, while remedyingto the drawbacks of the prior art compositions, also exhibits improvedabrasion and scratch-resistant properties.

[0015] The present invention also concerns a process for making suchabrasion or scratch-resistant coating compositions.

[0016] The present invention further concerns optical articles, inparticular optical lenses, coated with an abrasion or scratch-resistantcoating including a cured layer of the abrasion or scratch-resistantcoating composition.

[0017] According to the invention, there is provided an abrasion orscratch-resistant coating composition which comprises:

[0018] (A) a component which is the reaction product with oxalic acid ofat least one organometallic compound of formula:

R_(y) ¹—M (OR)_(x-y)   (I)

[0019] wherein, M is a metal, R is H or an alkyl radical, R¹ is achelating ligand, x is the valency of the metal, y is an integer atleast equal to 1 and x-y is at least equal to 1; and

[0020] (B) at least one organoalkoxysilane of formula:

R_(n) ³Si (OR²)_(4-n)   (II)

[0021] wherein, R² is an alkyl radical, R³ is an epoxidized monovalentorganic radical and n is an integer from 1 to 3;

[0022] or a mixture of the organoalkoxysilane of formula (II) with analkoxysilane of formula (II′)

[0023] R′_(n′)Si(OR″)_(4-n)  (II′)

[0024] wherein n′ is an integer from 0 to 3, preferably from 0 to 2(included), and

[0025] R″ is H or an alkyl radical or alkoxyalkyl radical, preferably aC₁-C₄ alkyl radical and R′ is a vinyl, (meth)acryl, aromatic, cyclic oraliphatic alkyl radical (preferably a C₁-C₄ alkyl radical).

[0026] Preferred alkoxysilanes of formula (II′) aretetra(methoxy)silane, tetra(ethoxy)silane, methyltrimethoxysilane,methyltriethoxysilane, dimethyldiethoxysilane, vinyldimethoxysilane,vinyltriethoxysilane, (meth)acryloxypropyltrimethoxysilane,(meth)acryloxypropyltriethoxysilane.

[0027] Preferably, component (B) comprises a major amount of theorganoalkoxysilane of formula (II).

[0028] Optionally, the inventive coating composition may be a partial ortotal hydrolyzate of components (A) and (B).

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

[0029] In component (A) of the coating composition the metal is ingeneral selected from the group consisting of Ti, Zr, Sc, Nb, V, Hf, Cr,Y, Al, Ge, Sn, Ta and W. Preferably the metal is Ti, Zr or Al and morepreferably Ti or Zr.

[0030] R is preferably a C₁-C₄ alkyl radical such as ethyl, propyl andbutyl.

[0031] R¹ is preferably a ligand produced from a compound of formulaL¹COCH₂COL² or L³COCH₂COOL⁴, wherein L¹, L², L³ and L⁴, are C₁-C₁₀ alkylgroups, preferably C₁-C₄ alkyl groups, and more preferably methyl andethyl groups.

[0032] Among the preferred ligands represented by R¹ there may be citedacetylacetonate, aliphatic aceto acetate, acetoacetones, acetylacetonesmethylacetoacetate, and ethylacetoacetate, being the most preferred.

[0033] Preferably also, in formula (I), y is equal to 2.

[0034] Among the most preferred component (A) there may be cited thereaction products of oxalic acid with titanium bis(acetylacetonato)diisopropoxide, zirconium bis(acetylacetonato) diisopropoxide,titanium (acetylacetonato)triisopropoxide and zirconium(acetylacetonato)triisopropoxide.

[0035] Component (A) of the compositions of the invention may beprepared by (1) mixing an organometallic compound of formula M(OR²)₄(III), wherein M and R² are as defined above, with a ligand producingcompound such as those defined above, at a temperature ranging fromambient temperature to 100° C. or more, and then (2) mixing to thereaction product of step (1) oxalic acid at ambient temperature.

[0036] Usually, a solvent is also used in step (2).

[0037] Among the appropriate solvents there may be cited methanol,ethanol, isopropanol, other aliphatic alcohols of low molecular weight,ethylacetate, methylethylketone and tetrahydropyrane.

[0038] Step (1) may last from 1 to 24 hours, depending upon the reactedcompounds and the reaction temperature.

[0039] In step (1) the amount of ligand producing compound is determinedin order to obtain a compound of formula (II) in which n is 1, 2 or 3,preferably 2.

[0040] Usually, there may be used 100 to 200 parts by weight of theligand producing compound per 100 parts by weight of the startingtetraalkoxyde compound of formula (III).

[0041] Step (2) will typically last for 5 to 15 minutes.

[0042] The amount of oxalic acid used in step (2) usually ranges from 10to 70, preferably 15 to 65 parts by weight based on 100 parts by weightof the starting tetraalkoxide compound of formula (III).

[0043] Nevertheless, an essential feature of the invention is that, instep (2), there is used at least an effective amount of oxalic acid, forexample a molar ratio of 2 or more of oxalic acid based on compound offormula (I) and in particular titanium or zirconium compounds of formula(I).

[0044] The organoalkoxysilanes of component (B) are advantageouslyepoxidized organoalkoxysilanes of formula:

[0045] in which R⁴ is a C₁-C₄ alkyl or alkoxy alkyl group, R⁵ is a C₁-C₆alkyl or aryl group, R⁶ is H or a methyl, m is 2 or 3, a is an integerfrom 1 to 6 and b is 0, 1 or 2.

[0046] Preferred epoxidized silanes areγ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane,γ-glycidoxypropyl methyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane and γ-glycidoxyethoxypropylmethyl dimethoxysilane.

[0047] The most preferred silane is γ-glycidoxypropyltrimethoxysilane(GLYMO).

[0048] In the abrasion or scratch-resistant coating compositions of theinvention, the organoalkoxysilanes may or may not be hydrolyzed.Hydrolysis of the silanes may be partial or complete. Advantageously theorganoalkoxysilanes are completely hydrolyzed.

[0049] The abrasion-resistant coating compositions of the invention mayfurther include other additives typically used in such abrasion orscratch-resistant coating compositions such as, surface-active agents,fillers, pigments, UV stabilizers and absorbers, antioxidants,cross-linking agents and hardening catalysts.

[0050] Any hardening catalyst known for their action in compositionssimlilar to those of the present invention may be used, such asdiamides, imidazoles, amines, organic sulfonic acids and their aminesalts, alkali metal salts of carboxylic acid, and cyclic amidines.

[0051] Preferably, the composition of the invention contains a smallamount of a surface-active agent.

[0052] The composition of the invention may also include mineralcolloidal fillers such as colloidal silica or colloidal fillersincreasing the refractive index of the resulting cured layer, inparticular to match as much as possible the refractive index of thesubstrate, specially when the substrate exhibits a high refractiveindex, in order to avoid optical defects such as interference fringes.

[0053] Such fillers may be oxides of Sb, Ti, Zr, Al, Ce, Sn, W andmixtures thereof, as well as mixed oxides (composite particles of theseoxides), in particular Ti/Zr, Ti/Zr/Sn and Sn/W.

[0054] The amount of colloidal filler in the composition of theinvention may be up to 50% by weight of the dry extract of thecomposition.

[0055] The present invention is also directed to a process for making anabrasion-resistant coating composition which comprises:

[0056] (1) reacting in solution an organometallic compound of formula(I) with an effective amount of oxalic acid to obtain a solution of areaction product of the organometallic compound with oxalic acid; and

[0057] (2) adding with mixing to the solution of the reaction product ofstep (2), an organo-alkoxysilane of formula (II).

[0058] Preferably, the process of making the present composition furthercomprises

[0059] (3) hydrolysing the mixture resulting from step (2).

[0060] In a further preferred embodiment of the process there isprovided an additional step (4) of adding a surface-active agent eitherto the mixture resulting from step (2) or step (3).

[0061] Hydrolysing step (3) may be a partial or complete hydrolysis ofthe mixture. Hydrolysing medium may be water or a mixture of water andalcohol.

[0062] The amount of oxalic acid used in step (1) usually ranges from 10to 70, preferably 15 to 65 parts by weight based on 100 parts by weightof corresponding tetraalkoxide compound of formula (III) from whichcompound of formula (I) is derived.

[0063] The oxalic acid addition and treatment is usually effected in ashort period of time of 5 to 15 minutes, preferably about 10 minutes atroom temperature.

[0064] The amount of organoalkoxysilanes of formula (II) in the presentcomposition usually ranges from 50 to 90, preferably 60 to 80 parts byweight based on 100 parts by weight of component (A).

[0065] The addition and mixing of the organoalkoxysilane of formula (II)is generally effected at room temperature within a period of 1 toseveral hours, preferably about 2 hours.

[0066] When, the present composition is hydrolyzed, hydrolysis can beeffected in the usual manner by addition of deionized water or a mixtureof deionized water and alcohol. Hydrolysis step, as well known, may lastfor several hours, for example about 2 hours. Preferably the amount ofwater used is such that a complete hydrolysis is obtained.

[0067] The other additives such as the surface-active agent are thenadded and mixed in the usual manner.

[0068] The present invention further concerns a plastic substrate coatedwith a abrasion-resistant cured layer of a coating composition of thepresent invention.

[0069] Suitable substrates are any desired plastic materials, forexample poly(meth)acrylates polythio(meth)acrylates, polystyrenes,polyurethanes and polycarbonates, and in particular poly(diethyleneglycol bis-allyl carbonate) such as the material commercialized underthe tradename CR-39® by PPG Industries.

[0070] The coating process may be any customary coating process, forexample immersion or dip coating, flow-coating, spin-coating,roll-coating, spray-coating or brush-coating.

[0071] The coating is applied in coating thicknesses of, for example, 1to 100 μm, preferably 1 to 20 μm and in particular 1 to 5 μm.

[0072] Curing of the compositions of the present invention is generallyeffected by heating at a temperature of 100 to 150° C. for 1 to severalhours. Preferably, curing comprises a precuring step at a temperature of50 to 70° C. for several minutes, usually 10 to 20 minutes, followed bya post-curing step at a temperature of 100 to 120° C. for at least onehour, usually 2 to 5 hours.

[0073] In a preferred embodiment of the present invention, the curedabrasion-resistant layer made of the coating composition of the presentinvention is used with a plastic substrate comprising an alreadydeposited cured abrasion-resistant layer made of an abrasion-resistantcoating composition. This abrasion resistant layer is preferably a(meth)acrylic layer or a polysiloxane layer. More preferably, theabrasion resistant layer is a polysiloxane layer obtained by curing acomposition comprising a hydrolyzate of silane compounds containing anepoxy group and at least two alkoxy groups.

[0074] The preferred already deposited cured abrasion resistant layercomprises at least one hydrolyzate of silane compounds containing anepoxy group and at least two alkoxy groups, colloidal silica and atleast one aluminum chelate compound. Such abrasion-resistant coatingcompositions and their use for providing a cured abrasion-resistantlayer on a plastic material substrate are disclosed in U.S. Pat. No.4,211,823 which is incorporated by reference.

[0075] Most preferred silane compounds are the same as component (B)defined previously.

[0076] The already deposited cured abrasion-resistant layer may furthercontains a colloidal filler or mixture of colloidal fillers as mentionedabove for the composition according to the invention.

[0077] Anti-abrasive coating compositions containing such colloidalfillers are disclosed for example in patents and patent applicationsU.S. Pat. No. 4,571,365; EP-A-730,168 and EP-A-526,975.

[0078] As previously mentioned, the amount of colloidal filler may be upto 50% by weight and, in the case of the polysiloxane underlayer in therange of from 30 to 50% by weight.

[0079] The cured abrasion-resistant layer of the abrasion-resistantcoating composition according to the present invention is placed on topof the pre-deposited cured abrasion-resistant layer defined just above.The pre-deposited cured abrasion-resistant layer commonly has athickness ranging from 1 to 20 μm and preferably 1 to 5 μm.

[0080] It has been found that, when used conjointly with a curedabrasion-resistant underlayer as described above, the curedabrasion-resistant layer according to the invention results in a plasticarticle coated with a hard-coat having an exceptional combination ofabrasion-resistant properties as measured by Bayer test and Steel Wooltest.

[0081] In preferred embodiments of the invention the substrate is anoptical article and in particular an ophtalmic lens.

[0082] In the following examples, otherwise stated, all parts andpercentages are by weight.

[0083] Bayer abrasion-resistance test and Steel Wool scratch-resistancetest were performed as follows:

BAYER ABRASION RESISTANCE TEST

[0084] The abrasion resistance of a coating was examined by subjectingthe coated lens to a fixed cycle of oscillating sand abrasion, similarto ASTM#F735-81 using approximately 500 grams of aluminium oxide (Al₂O₃)ZF Anlundum 152412 supplied by Specialty Ceramic Grains (former NortonMaterials)/New Bond Street, PO Box 15137 Worcester, Mass. 01615-00137.The haze before and after abrasion was measured using a PacificScientific Hazemeter XL-211.

[0085] The change in the haze measurement before and after abrasion ofthe uncoated and coated lenses was tested. The ratio of the uncoatedlens haze measurement to the coated lens haze measurement determines theperformance of the test lens. The higher the ratio, the better theperformance of the coating. Results of at least 3 test lenses areaveraged for a final ratio.

STEEL WOOL SCRATCH RESISTANCE TEST

[0086] The “cutting” scratch resistance of the coatings was examined bysubjecting the coated lens to abrasion similar to that described in U.S.Pat. No. 4,084,021. The device described in the patent was modified torock the sample in an arch equivalent to a 600 diopter radius, whichmatches the front curve of the test speciments. “000” steel wool wasused with the grain parallel to the rocking motion. The amount ofabrasion was quantified by measuring the transmitted light haze of theabraded specimen, before and after abrasion, as described in the BayerAbrasion Resistance Test. The change in haze is reported in the resultstable. A low change in haze indicates a high performance of the coating.

EXAMPLE 1

[0087] 40 g of titanium tetraisopropoxide were mixed with 80 g of ethylaceto acetate and heated at 90-100° C. under nitrogen blanket for twohours. A mixture of 12.7 g of oxalic acid and 50 g of ethanol was thenadded to the above mixture and mixed for 10 minutes. Thereafter, 50 g ofglycidoxypropyltrimethoxysilane (GLYMO) were added and mixed for 2hours. A mixture of 75 g of deionized water and 50 g of ethanol wasadded and mixed for 2 hours. 100 g of diacetone alcohol was then added.Finally, 0.4 g of a surface-active agent was added and mixed.

[0088] The resulting coating composition was applied by dip coating on aCR-39® lens substrate, precured for 15 minutes at 60° C. and postcuredfor 4 hours at 110° C.

[0089] The refractive index of the cured abrasion resistant layer wascalculated to be 1.57.

[0090] The results of the Bayer and Steel Wool tests are reported inTable I.

[0091] As shown by the results in Table I, the cured abrasion-resistantlayer of the composition according to the invention exhibitsexceptionally high Bayer values.

EXAMPLE 2

[0092] 40 g of titanium tetraisopropoxide were mixed with 40 g of ethylaceto acetate for 24 hours at room temperature. A mixture of 12.7 g ofoxalic acid and 50 g of ethanol was then added to the above mixture andmixed for 10 minutes. Thereafter, 50 g GLYMO were added and mixed for 2hours. A mixture of 75 g of deionized water and 50 g of ethanol wasfurther added and mixed for 2 hours. 100 g of diacetone alcohol wereadded. Finally, 0.4 g of a surface-active agent were added and mixed.

[0093] The resulting coating composition was applied by dip coating on aCR-39® lens substrate, precured for 15 minutes at 60° C. and postcuredfor 4 hours at 110° C.

[0094] The calculated refractive index was 1.57.

[0095] The results of the Bayer and Steel Wool tests are reported inTable I.

[0096] As shown by the results in Table I, the resulting curedabrasion-resistant layer exhibits exceptionally high Bayer values.

EXAMPLE 3

[0097] 40 g of titanium tetraisopropoxide were mixed with 40 g of ethylaceto acetate for 24 hours at room temperature. A mixture of 12.7 g ofoxalic acid and 50 g of ethanol was added to the above mixture and mixedfor 10 minutes. 50 g of GLYMO were added and mixed 2 hours. A mixture of75 g of deionized water and 50 g of ethanol was added and mixed for 2hours. 100 g of diacetone alcohol were added. Finally, 0.4 g ofsurface-active agent was added and mixed.

[0098] This abrasion-resistant coating composition was then applied bydip coating onto a hard coat layer formed on a CR-39® lens substrate,precured 15 minutes at 60° C. and postcured for 4 hours at 110° C.

[0099] The hard coat layer was a cured layer resulting from curing of anabrasion-resistant coating composition according to U.S. Pat. No.4,211,823 comprising basically, in percent by weight: GLYMO 22.2 0.1 NHCl  5.1 Nalco 1034A Aqueous Colloidal Silica (34 weight % dry extract)31.6 Solvent 39.5 and a catalytic amount of (Aluminum acetylacetonate)

[0100] The remaining being usual surface-active agent and opticaladditives.

[0101] The results of the Bayer and steel wool tests are reported inTable I.

[0102] These results show that there is obtained exceptional goodbalance between the Bayer and the Steel Wool tests results.

EXAMPLE 4

[0103] 40 g of titanium tetraisopropoxide were mixed with 40 g of ethylaceto acetate for 24 hours at room temperature. A mixture of 12.7 g ofoxalic acid and 50 g of ethanol was added to the above mixture and mixedfor 10 minutes. 50 g of GLYMO were added and mixed 2 hours. 200 g ofethanol were added. Finally, 0.4 g of surface-active agent was added andmixed. This coating composition was applied by dip coating onto a CR-39®lens substrate, precured for 15 minutes at 60° C. and postcured for 4hours at 110° C. Calculated refractive index was 1.57. The results ofthe Bayer and Steel Wool tests are reported in Table I.

[0104] These results show that a good balance in Bayer and Steel Woolabrasion-resistance tests is obtained even when the composition is nothydrolyzed with addition of water.

EXAMPLE 5

[0105] 65 g of commercially available titanium chelate Dupont Tyzor AA®of the formula [CH₃COCH₂COCH₃]Ti[OCH(CH₃)₂]₂ were mixed with 60 g ofethanol and 12.7 g of oxalic acid for 10 minutes. 50 g of GLYMO wereadded and mixed for 2 hours. Next, a solution of 75 g of deionized waterand 128 g of ethanol was added and mixed for 2 hours. 50 g of diacetonealcohol were added and finally 0.3 g of surface-active agent was addedand mixed. This coating composition was applied by dip coating onto aCR-39® lens substrate, precured for 15 minutes at 60° C. and postcuredfor 4 hours at 110° C. Calculated refractive index was 1.57.

[0106] The results of the Bayer and Steel Wool tests are reported inTable I.

EXAMPLE 6

[0107] 65 g of Dupont Tyzor AA® were mixed with 60 g of ethanol and 12.7g of oxalic acid for 10 minutes. 50 g of glycidoxypropyltrimethoxysilanewere added and mixed for 2 hours. 128 g of ethanol and 50 g of diacetonealcohol were added and finally 0.3 g of surface-active agent was addedand mixed. This coating composition was applied by dip coating onto aCR-39® lens substrate, precured for 15 minutes at 60° C. and postcuredfor 4 hours at 110° C. Calculated refractive index was 1.57.

[0108] The results of the Bayer and Steel Wool tests are reported inTable I.

EXAMPLE 7

[0109] 40 g of titanium tetraisopropoxide were mixed with 40 g of ethylaceto acetate for 24 hours at room temperature. A mixture of 25.4 g ofoxalic acid and 70 g of ethanol was added to the above mixture and mixedfor 10 minutes. 50 g of glycidoxypropyltrimethoxysilane were added andmixed for 2 hours. 100 g of ethanol and 75 g of deionized water wereadded and mixed for 2 hours. 50 g of diacetone alcohol were added andfinally 0.4 g of surface-active agent was added and mixed. This coatingcomposition was applied by dip coating onto a CR-39® lens substrate,precured for 15 minutes at 60° C. and postcured for 4 hours at 110° C.Calculated refractive index was 1.55.

[0110] The results of the Bayer and Steel Wool tests are reported inTable I.

EXAMPLE 8

[0111] 40 g of titanium tetraisopropoxide were mixed with 40 g of ethylaceto acetate for 24 hours at room temperature. A mixture of 6.3 g ofoxalic acid and 70 g of ethanol was added to the above mixture and mixedfor 10 minutes. 50 g of glycidoxypropyltrimethoxysilane were added andmixed for 2 hours. 100 g of ethanol and 75 g of deionized water wereadded and mixed for 2 hours. 50 g of diacetone alcohol were added andfinally 0.4 g of surface-active agent was added and mixed. This coatingcomposition was applied by dip coating onto a CR-39® lens substrate,precured for 15 minutes at 60° C. and postcured for 4 hours at 110° C.Calculated refractive index was 1.58.

[0112] The results of the Bayer and Steel Wool tests are reported inTable I.

Comparative example A

[0113] 40 g of titanium tetraisopropoxide were mixed with 40 g of ethylaceto acetate for 24 hours at room temperature. A mixture of 18.2 g ofitaconic acid and 50 g of ethanol was added to the above mixture andmixed for 10 minutes. 50 g of glycidoxypropyltrimethoxysilane were addedand mixed for 2 hours. 50 g of ethanol and 75 g of deionized water wereadded and mixed for 2 hours. 50 g of diacetone alcohol were added andfinally 0.4 g of surface-active agent was added and mixed. This coatingcomposition was applied by dip coating onto a CR-39® lens substrate,precured for 15 minutes at 60° C. and postcured for 4 hours at 110° C.

[0114] The results of the Bayer and Steel Wool tests are reported inTable I.

[0115] As shown by these results, this prior art composition results inan hard coat layer exhibiting much lower bayer values than thecompostion of the present invention.

Comparative example B

[0116] 40 g of titanium tetraisopropoxide were mixed with 40 g of ethylaceto acetate for 24 hours at room temperature. A mixture of 16.25 g offumaric acid and 50 g of ethanol was added to the above mixture andmixed for 10 minutes. 50 g of GLYMO were added and mixed for 2 hours.100 g of ethanol and 75 g of deionized water were added and mixed for 1hour before the liquid gelled irreversibly.

Comparative example C

[0117] 40 g of titanium tetraisopropoxide were mixed with 40 g of ethylaceto acetate for 24 hours at room temperature. A mixture of 29.4 g of1,2,4-benzenetricarboxylic acid and 50 g of ethanol was added to theabove mixture and mixed for 10 minutes. 50 g of GLYMO were added andmixed for 2 hours. 50 g of ethanol and 75 g of deionized water wereadded and mixed for 2 hours. 50 g of diacetone alcohol were added and,finally, 0,4 g of surface-active agent was added and mixed. This coatingcomposition was applied by dip coating onto a CR-39® lens substrate,precured for 15 minutes at 60° C. and postcured for 4 hours at 110° C.

[0118] The Bayer and Steel Wool abrasive tests values are reported inTable I. These results show that the Bayer test value is not acceptable.TABLE I Example n° BAYER STEEL WOOL 1 280.3 34.66 2 825.0 42.06 3 211.150.27 4 11.80 35.59 5 129.50 35.64 6 25.23 46.95 7 122.67 27.89 8 134.8845.93 (comparative) A 2.10 8.36 (comparative) C 0.75 25.27

1. An abrasion or scratch resistant coating composition comprising: (A)a component which is the reaction product with oxalic acid of at leastone organometallic compound of formula: R_(y) ¹—M (OR)_(x-y)   (I)wherein, m is a metal r is h or an alkyl radical, R¹ is a chelatingligand, x is the valency of the metal, y is an integer at least equal to1 and x-y is at least equal to 1; and (B) at least oneorganoalkoxysilane of formula: R_(n) ³Si (OR²)_(4-n)  (II) wherein, R²is an alkyl radical, R³ is an epoxidized alkyl group and n is an integerfrom 1 to 3, or a mixture of the organoalkoxysilane of formula (II) withan alkoxysilane of formula (II′) R′_(n′)Si(OR″)_(4-n) (II′) wherein n′is an integer from 0 to 3, R″ is H, an alkyl radical or an alkoxyalkylradical, and R′ is a vinyl, (meth)acryl, aromatic, cyclic or aliphaticalkyl radical.
 2. An abrasion-resistant coating composition according toclaim, 1 wherein M is selected from Ti, Zr, Sc, Nb, V, Hf, Cr, Y, Al,Ge, Sn, Ta, and W.
 3. An abrasion-resistant coating compositionaccording to claim 1 , wherein M is Ti or Zr.
 4. An abrasion-resistantcoating composition according to claim 1 , wherein R¹ is a ligandproduced from a compound of formula L¹COCH₂COOL² or L³COCH₂COOL⁴,wherein L¹, L², L³ and L⁴ are C₁-C₄ lower alkyl groups.
 5. Anabrasion-resistant coating composition according to claim 1 , whereinthe organoalkoxysilane has formula:

wherein R⁴ is an alkyl or alkoxy alkyl group having 1 to 4 carbon atoms;R⁵ is an alkyl or aryl group having 1 to 6 carbon atoms; R⁶ is H or amethyl group, m is 2 or 3, a is an integer from 1 to 6 and b is 0, 1 or2.
 6. An abrasion-resistant coating composition according to claim 5 ,wherein the organoalkoxysilane is selected from the group consisting ofγ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane,γ-glycidoxypropylmethyldimethoxysilane,γ-glycidoxypropylmethyldiethoxysilane andγ-glycidoxyethoxypropylmethyldimethoxysilane.
 7. An abrasion-resistantcoating composition according to claim 1 , wherein components (A) and(B) are further partially or fully hydrolyzed.
 8. A process for makingan abrasion or scratch-resistant coating composition comprising: (1)reacting with oxalic acid at least one organometallic compound offormula: R_(y) ¹—M (OR)_(x-y) wherein, M is a metal, R is H or an alkylradical, R¹ is a chelating ligand, x is the valency of the metal, y isan integer at least equal to 1 and x-y is at least equal to 1; and (2)mixing to the reaction product of (1) at least one organoalkoxysilane offormula: R_(n) ³Si (OR²)_(4-n) wherein, R² is an alkyl radical, R³ is anepoxidized alkyl group and n is an integer from 1 to
 3. 9. The processaccording to claim 8 , further comprising the step of (3) partially orcompletely hydrolyzing the mixture obtained in step (2).
 10. The processof claim 8 , further comprising the step (3) of adding and mixing asurface-active agent.
 11. The process of claim 8 , wherein M is selectedfrom Ti, Zr, Sc, Nb, V, Hf, Cr, Y, Al, Ge, Sn, Ta, and W.
 12. Theprocess of claim 8 , wherein M is Ti or Zr.
 13. The process of claim 8 ,wherein R¹ is a ligand produced from a compound of formula L¹CQCH₂COOL²or L³COCH₂COOL⁴, wherein L¹, L², L³ and L⁴ are C₁-C₄ lower alkyl groups.14. The process of claim 8 , wherein the organoalkoxysilane has formula:

wherein R⁴ is an alkyl or alkoxy alkyl group having 1 to 4 carbon atoms;R⁵ is an alkyl or aryl group having 1 to 6 carbon atoms ; R⁶ is H or amethyl group, m is 2 or 3, a is an integer from 1 to 6 and b is 0, 1 or2.
 15. The process of claim 8 , wherein in step (1) the amount of oxalicacid reacted with the organometallic compounds ranges from 10 to 70parts by weight based on 100 parts by weight of correspondingtetraalkoxide compound from which compound of formula (I) is derived.16. The process of claim 8 , wherein the amount of organoalkoxysilanesadded and mixed in step (2) ranges from 50 to 90 parts by weight percenton 100 parts by weight of component (A).
 17. A plastic materialsubstrate coated with a cured layer of an abrasion or scratch resistantcoating composition as set forth in claim 1 .
 18. A plastic materialsubstrate having a first abrasion-resistant coating comprising a(meth)acrylic or polysiloxane cured material and an additional curedabrasion-resistant layer of the composition as set forth in claim 1deposited on top of the first coating.
 19. The plastic materialsubstrate of claim 18 , wherein the polysiloxane coating is a coatingobtained from a hydrolyzate of a silane compound containing an epoxygroup and at least two alkoxy groups directly linked to silicon.
 20. Theplastic material substrate according to claim 19 , wherein the silanecompound has formula:

wherein R⁴ is an alkyl or alkoxy alkyl group having 1 to 4 carbon atoms; R⁵ is an alkyl or aryl group having 1 to 6 carbon atoms; R⁶ is H or amethyl group, m is 2 or 3, a is an integer from 1 to 6 and b is 0, 1 or2.
 21. A plastic material substrate comprising a first cured layer of anabrasion-resistant composition including at least one hydrolyzate ofsilane compounds containing an epoxy group and at least two alkoxygroups, colloidal silica and at least one aluminum chelate compound,wherein an additional cured abrasion-resistant layer of the compositionas set forth in claim 1 is deposited on top of the first cured layer.22. An ophtalrnic lens comprising a plastic material substrate having atleast one face coated with a cured layer of an abrasion-resistantcomposition as set forth in claim 1 .
 23. An opthalmic lens comprising aplastic material substrate coated on at least one face with a firstcured layer of an abrasion-resistant composition including at least onehydrolyzate of silane compounds containing an epoxy group and at leasttwo alkoxy groups, colloidal silica and at least one aluminum chelatecompound, and an additional cured abrasion-resistant layer of anabrasion-resistant composition as in claim 1 , deposited on top of saidfirst cured layer.